Louis Hayward

as Philip 'Scotty' Grayson

Dennis O'Keefe

as Daniel F. O'Hara

Louise Allbritton

as Dr. Anastasia 'Toni' Neva

Carl Esmond

as Dr. Ritter von Stolb

Onslow Stevens

as Igor Braun

Raymond Burr

as Krebs

Art Baker

as Dr. Frederick Townsend

Lowell Gilmore

as Dr. William Forrest